1. Field of the Invention
This invention relates to a throttle-valve position sensing system for use with an internal combustion engine having an induction passage provided therein with a throttle valve and, more particularly, to such a system for sensing the most closed position possible for the throttle valve.
2. Description of the Prior Art
In order to detect engine deceleration and idling conditions, throttle-valve closed position sensors have been used which include an idle switch adapted to provide a signal when the throttle valve is in its closed positions. Such an idle switch has a contact fixed at a suitable position and a contact movable, with rotation of the throttle valve, into and out of contact with the fixed contact. The movable contact moves into contact with the fixed contact when the throttle valve is in its closed positions.
However, such conventional throttle-valve closed position sensors suffer from certain disadvantages. First, they cannot detect engine deceleration and idling conditions in case where a fast-idle mechanism is used to force the throttle valve to remain open at low engine temperatures for fast engine warming. Second, the accuracy with which they detect engine deceleration and idling conditions is greatly affected by secular fluctuation.
The present invention provides a system which can sense the most closed position possible for a throttle valve.